Astronomy Day is an annual event in the United States intended to provide a means of interaction between the general public and various astronomy enthusiasts, groups and professionals.
This event was started in 1973 by Doug Berger, the president of the Astronomical Association of Northern California. His intent was to set up various telescopes in busy urban locations so that passersby could enjoys views of the heavens. Since then the event has expanded and is now sponsored by a number of organizations associated with astronomy.
Astronomy Day also forms part of National Astronomy Week, which begins on the preceding Monday.
Originally, Astronomy Day occurred on a Saturday between mid-April and mid-May, and was scheduled so as to occur at or close to the first quarter Moon. In 2007, an autumn rendition of Astronomy Day was added. It was scheduled to occur on a Saturday between mid-September and mid-October so as to be on or close to the first quarter Moon.
2014 - Season: Spring; Astronomy Day: May 10; First Quarter Moon: May 7; Season: Fall; Astronomy Day: October 4; First Quarter Moon: October 1.
In 2018 Astronomy Day in USA falls on April 21.